Preclinical evaluation of anti-rheumatic drugs in a non-human primate model of arthritic disease

Anti-carbamylated protein antibodies precede disease onset in monkeys with collagen-induced arthritis

Background

Rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA) and anti-carbamylated protein (anti-CarP) antibodies are rheumatoid arthritis (RA)-associated autoantibodies. Besides their presence in human serum, anti-CarP antibodies have also been described in rodent models of arthritis, while ACPA are not consistently detectable. Data on these RA-associated autoantibodies in primates are not available. Therefore, we investigated the presence of RF, anti-CarP antibodies and ACPA in rhesus monkeys before and after collagen-induced arthritis immunizations.

Methods

In previous studies, arthritis was induced in groups of rhesus monkeys by immunisation with collagen following pre-treatment with placebo, abatacept or Roactemra. Previously collected serum was used to measure, autoantibodies by ELISA, detecting anti-CarP antibodies, RF-IgM and antibodies against CCP2, citrullinated myelin basic protein and citrullinated fibrinogen.

Results

Out of the three autoantibodies, only anti-CarP antibodies were detectable in resus monkeys with arthritis. RF-IgM and ACPA were undetectable and below the detection limit of the ELISA. The level of anti-CarP antibodies increases over time and, similar to in humans and mice, these autoantibodies were already detectable before clinical disease onset. Furthermore, preventive treatment with abatacept (CTLA4/IgG1-Fc fusion protein) inhibited the development of anti-CarP antibodies after immunization, while this was less evident for preventive Roactemra (anti-IL6-receptor) treatment. Moreover, disease progression was only reduced following abatacept treatment.

Conclusion

Rhesus monkeys develop anti-CarP antibodies upon induction of collagen-induced arthritis, while we were unable to detect RF or ACPA. Also, the development of anti-CarP antibodies could be inhibited by preventive abatacept treatment.

Clinical efficacy of a new CD28-targeting antagonist of T cell co-stimulation in a non-human primate model of collagen-induced arthritis

T cells have a central pathogenic role in the aetiopathogenesis of rheumatoid arthritis (RA), and are therefore a favoured target of immunotherapy aiming at physical or functional elimination. Here we report an efficacy test of FR104, a new co-stimulation inhibitor directly targeting CD28 on T cells, in a translationally relevant model, the rhesus monkey model of collagen-induced arthritis (CIA). As a relevant comparator we used abatacept [cytotoxic T lymphocyte antigen immunoglobulin (CTLA Ig)], an antagonist of CTLA-4 binding to CD80/86 clinically approved for treatment of RA. Treatment with either compound was started at the day of CIA induction. Although FR104 previously demonstrated a higher control of T cell responses in vitro than abatacept, both compounds were equally potent in the suppression of CIA symptoms and biomarkers, such as the production of C-reactive protein (CRP) and interleukin (IL)-6 and anti-collagen type II (CII) serum antibody (IgM/IgG). However, in contrast to abatacept, FR104 showed effective suppression of CII-induced peripheral blood mononuclear cell (PBMC) proliferation. The current study demonstrates a strong potential of the new selective CD28 antagonist FR104 for treatment of RA.

Comparative analysis of inflammatory infiltrates in collagen-induced arthritis, kidney graft rejection and delayed-type hypersensitivity in non-human primates

OBJECTIVES

Non-human primates are immunologically closely related to humans providing relevant models of inflammatory disorders often used to evaluate new immunomodulating therapies. The aim of the study was to compare inflammatory infiltrates of acute graft rejection (AR) and collagen-induced arthritis (CIA) to delayed-type hypersensitivity (DTH) reactions as the latter model may serve as a less invasive animal model.

MATERIALS AND METHODS

Tissue samples of AR, CIA and DTH were obtained from rhesus monkeys used in several pre-clinical studies. The infiltrate composition was determined by immunohistochemical analysis.

RESULTS

The infiltrates in AR consisted of T cells, macrophages and B cells. The presence of lymphoid structures in AR suggested ongoing intragraft immune activation. The synovia of CIA contained predominantly macrophages and few T cells. The DTH infiltrates were dominated by T cells when the challenged was ovalbumin (OVA) and by macrophages when the challenge was tetanus toxoid (TT).

CONCLUSIONS

The histology of AR resembles aspects of DTH to OVA while that of CIA showed similarities of the DTH to TT. The DTH reaction could serve as a model to study immunomodulating drugs for acute rejection and the acute inflammatory phase of autoimmunity.